Field of the Invention
The present invention relates to a fuel cell stack including a stacked body formed by stacking a plurality of power generation cells for generating electrical energy. Each of the power generation cells is formed by stacking an electrolyte electrode assembly and separators. Each of the electrolyte electrode assemblies includes an electrolyte and a pair of electrodes provided respectively on both sides of the electrolyte.
Description of the Related Art
For example, a solid polymer electrolyte fuel cell employs a polymer ion exchange membrane as an electrolyte membrane. In the fuel cell, the electrolyte membrane is interposed between an anode and a cathode to form a membrane electrode assembly (MEA). The membrane electrode assembly and separators sandwiching the membrane electrode assembly make up a power generation cell for generating electricity. In use, typically, a predetermined number of the power generation cells are stacked together to form a fuel cell stack, which is mounted in a vehicle, for example.
With such a fuel cell stack, for obtaining a desired power generating capability, a predetermined number (e.g., from several tens to several hundreds) of the power generation cells are stacked, and there exists a need to detect whether or not each of the power generation cells has a desired power generating capability. For this purpose, in general, cell voltage monitoring terminals, which are disposed on the separators, are connected to a voltage detecting device (cell voltage monitor), and during power generation, an operation is performed to detect the cell voltage of each of the power generation cells.
For example, as disclosed in Japanese Patent No. 3870719, a fuel cell is known having a connection structure for connecting cell-voltage monitoring connectors to the cells thereof. With this fuel cell, one terminal from among a plurality of cell-voltage monitoring connectors is placed in contact with a separator of one of the cells that make up the fuel cell. In addition, another terminal is placed in contact with a separator, which is of the same polarity as the separator contacting with the one terminal, of another cell that differs from the one cell. On peripheral edge portions of the separators with which the terminals are placed in contact, portions are formed that protrude beyond peripheral edge portions where the terminals are not connected, and the terminals and the separators are placed in contact with each other at the protruding portions.
To inspect the voltage of one of the cells, monitoring is performed between a separator of the one cell and a separator of the next cell that is the same polarity. Consequently, in the case that the voltage of the last cell of the cell stack body is to be inspected, since there is no such next cell, the cell voltage of the last cell cannot be inspected. For this reason, a conductive cover plate (dummy separator), which is of the same shape as the separators to which terminals of the cell-voltage monitoring connector are connected, is disposed on an end of the cell stack body of the fuel cell. Stated otherwise, the terminal of the cell-voltage monitoring connector is connected to the cover plate. Therefore, by inspecting a potential difference between the cover plate and the separator of the last cell, the cell voltage of the last cell can be monitored.